Questions tagged [weather]
Weather means the atmospheric conditions, including wind, temperature and precipitation, in a specific area at a specific time.
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Is the pressure change due to volcanic activity a concern?
The recent eruption of the Hunga Tonga–Hunga Ha'apai sent a shockwave so massive that it got picked all over the world by weather stations.
This is the pressure detected one in Italy (source), where ...
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1answer
44 views
Formation of Clouds in High Pressure Systems (Western Australia - Perth) [closed]
High pressure systems are normally correlated with stable atmospheric conditions with little to no cloud cover, but due to this minimal cloud cover, doesn't that open up the ocean / ground moisture to ...
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1answer
152 views
How far does the lightning detector work at an AWOS station, as reported in a METAR?
I noticed on my local airport's METAR that there was distant lightning to the east. I am near Kansas City. When I looked at radar, the only possible system that could produce lightning was in the St. ...
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2answers
270 views
What is considered to be a flight into known Icing?
I am aware that flight into known icing is prohibited if your aircraft is not suitable to fly in icing conditions (unless e.g.: FIKI,...). Given the following example I am wondering if it would be ...
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1answer
93 views
What is Tendency of RVR?
What does tendency of RVR (Runway Visual Range) mean and why down and up have the same values?
This is from AWOS(Automated Weather Observing System)
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1answer
379 views
What does AO2A in the remarks of a METAR mean?
I am familiar with AO2 in the METAR remarks as described in this answer, which means the station is automated and has a precipitation discriminator. I have noticed sometimes there is AO2A in the ...
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1answer
167 views
Will a jet flown on a parabolic arc reach its highest altitude on a warm day or a cold one?
In level flight, on cold days jet-powered planes can fly higher because the air is denser. However, at the same time the true airspeed is lower because of the denser air.
At warmer temperatures a ...
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Why would "hot gases" from a volcano damage helicopter rotors?
In the ongoing story about someone trying to rescue dogs from a volcano with a drone, I keep seeing variations of this claim repeated:
Spanish authorities have dropped food down to the dogs with ...
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1answer
82 views
Station pressure vs. reported altimeter
I must be missing something big. Page 12-5 of the PHAK tells me that a station at 5,000 feet above sea level would convert its 24.92 pressure reading to 29.92. I understand that this helps to track ...
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Why are pressure levels raised on warm days?
As I'm studying for the PPL knowledge exam, I had the following note:
Pressure levels are raised on warm days and the indicated altitude is lower than true altitude.
(source: AOPA)
But I don't quite ...
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What is inflated wind speed?
According to NOAA, inflated wind speed is "the true wind speed (in knots) adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, ...
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2answers
147 views
Best way to forecast density altitude?
Let's say I'm planning a day trip from a low elevation home base to a warm, mountainous location. I wake up early, check the weather, do performance calculations based on current METARs, and decide to ...
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Why is the minimum for VFR 1000/3 while there are VFR weather minimums for every single airspace?
It seems like I have a concept error here. I don't understand why "the VFR min is 1000/3" when I think I would need to check in which airspace I am to then check for its respective weather ...
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Effect of heat and humidity on take off, descent, climb, and cruise
I am aware of this question, this resource (phak), and this resource that explains the science, but I am looking for a more straightforward answer.
I am student pilot and there's a lot of literature ...
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1answer
112 views
What kind of weather conditions would produce turbulence with an intensity of 90 feet per second?
This is the official documentation that we found regarding current commercial airplane design criteria; https://www.law.cornell.edu/cfr/text/14/25.341
It says the criteria for continuous turbulence is ...
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1answer
154 views
Why does the Winds Aloft ‘For Use Time’ start before the ‘Valid Time’?
Why is it that a winds aloft forecast normally has a "valid time" that comes in the middle of the "for use" time range? Why don't they just state the valid time as the beginning of ...
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1answer
76 views
What does Region @TOP mean on the aviationweather.gov website?
When looking at raw METAR data on the aviation weather center, "@TOP" appears in the text box where you can type identifiers. What does TOP mean?
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2answers
232 views
Do airliners get substantially different weather briefings from the rest of us?
Southwest Airlines flights were delayed and cancelled this week due to an outage in their third-party weather provider. I understand if they have a streamlined business process for getting weather ...
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158 views
How can I calculate the "stability state" of air from a given set of data?
I would like to know the answer for the above question, it is about how to find whether atmosphere is stable or unstable using DALR (dry adiabatic lapse rate), SALR (saturated adiabatic lapse rate) ...
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1answer
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What is the red barb for in the NOAA weather briefing?
Wind barbs are well-defined symbols, but I noticed in my WX briefing that there are now occasional red barbs in the chart.
The red appears on both the 5kt and 10kt barbs, and sometimes for largest ...
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3answers
1k views
Can gusts be reported as lower than wind speed?
KADS 072350Z 31030G20KT 13SM SKC 24/02 A2980
I’ve never seen a negative gust factor before. Is that a real thing (and if so, what does it mean), or did someone just make a typo?
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1answer
109 views
When was the last time the US Standard Atmosphere 1976 was updated?
I imagine due to slight changes in Earth's atmosphere or more accurate instrumentation it's been updated at least once, but also because it's understood to be a less precise model we might not have ...
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1answer
107 views
How to get an accurate time of arrival to the en-route alternate airport during flight planning?
I was thinking about accurate criteria of selecting en-route alternate (ERA) weather from ground (planning stage) especially for ERA 3% contingency flight plan.
As we all know we should care about one ...
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2answers
1k views
Can I derive the wind speed and direction? [duplicate]
If I know the IAS and GS (with directional components) of an aircraft, can I derive the wind speed and direction?
I'm working on an application that simulates the flight of an aircraft. Another ...
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1answer
70 views
What are the Requirements for the implimentation of Low Visibility Procedures at an airport?
So I was wondering if the RVR at an airport is reported above CAT I conditions for eg 1400 Meters etc but the Visibility is 50 to 100 Meters then would the pilots carry out non instrument approach or ...
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1answer
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Why are the airport pressure values for "altitude" (inHg) and "sea level" (mb) slightly different on the NOAA web sites?
If one looks, for example, at the NOAA web site for Denver International Airport we see (at the time of posting this question) the Pressure/Altimeter is 29.78 inHg, the Pressure/sea level is 1006.1 mb ...
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0answers
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A scenario question regarding meteorology
In the image attached, I’m struggling to find out why the answer is the way it is; maybe is me not being able to visualise it, but some help would be greatly appreciated.
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1answer
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What causes Gusty winds? ( Meteorlogy) [closed]
I was wondering why winds can become gusty. I know that gusty winds tend to be related with frontal passage. Thanks : )
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3answers
174 views
What weather should we expect when temperature and dew point are similar?
What should i expect during my flight planning when i see both temperature and dew point are the same?
I understand there will be fog but what else? could it mean icing? any difference between 20/20 ...
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1answer
88 views
Why is cloud base estimation taught in Fahrenheit?
I've seen the formula for estimating cloud base consistently presented using Fahrenheit temperature and dewpoint (for example, see PHAK 12-14; Jeppesen also teaches it this way):
$$
\mathrm{cloud\:...
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2answers
175 views
How can I calculate ambient air pressure from flight data?
I am playing around with data collected during a flight. I would like to find out the (real, not ISA) ambient air pressure for each data point, since it is not reported in the spread sheet containing ...
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1answer
108 views
How can air stability be predicted?
After several weeks of being grounded due to low clouds, I was looking forward to the cool air, clear skies, high pressure and light winds that arrived this morning as forecasted. However, there is an ...
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1answer
175 views
What is the difference between the WSUSnn IDs used in convective SIGMETs?
When NOAA issues a convective SIGMET, it falls under one of three bulletin IDs: WSUS31, WSUS32, or WSUS33. Below are three examples from the current forecast.
WSUS31:
...
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1answer
440 views
What is the difference between mist and haze in terms of relative humidity?
I am an aviation meteorologist and I struggle to distinguish the two of them.
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1answer
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Where can I listen online to live VOLMET broadcasts?
Are there sites that stream live VOLMET broadcasts? I need to listen to the format but haven't have the time to put together an amateur radio.
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2answers
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What do pilots landing on aircraft carriers do when the ship is not visible due to weather?
Say an aircraft takes off of a carrier to do a mission somewhere, and upon returning to the carrier the pilot comes to find that a thick layer of fog has formed just above the surface of the water in ...
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2answers
258 views
Does DA/DH refers to ceiling?
If airport is reporting FEW001 or SCT001 and RVR is above 600m, does it means that there will be no LVO because ceiling is defined as more than 4/8 and DA/DH will be more than 100ft because DA/DH is ...
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1answer
60 views
Are AWOS data open for commercial use? [closed]
I 've found out this great website where you can get historical AWOS weather data. I would like to use it for a commercial application but I don't find any data license. Do you know if the AWOS data ...
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1answer
98 views
Where is there an FAA source that states that squall lines are non-frontal?
There's a question in the FAA commercial question bank that indicates that squall lines are nonfrontal, and the reference for the question points to the Aviation Weather Advisory Circular.
The word, &...
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4answers
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Can the "G" and "VRB" wind conditions be combined in METARs?
I have never seen the "VRB" (for wind direction variations < 60°; e.g. VRB12003KT) and "G" annotation (for gusts > 10KT wind speed difference; e.g. 12003GT30KT) being combined in a METAR.
Until ...
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1answer
74 views
How would a pilot apply the information found on a 500 Millibar Vorticity chart to a flight?
The U.S. Flight Service website has these weather products listed:
I have circled the 500 Millibar Vorticity Charts. I've been a pilot for 10+ years and have never heard mention of this chart by ...
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2answers
154 views
Is AMDAR a required system on aircraft?
I was intrigued by the assertion that COVID-19 depressing commercial aviation has lead to lower quality weather forecasting
The aircraft observations are a key piece in the jigsaw of national and ...
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1answer
187 views
Does a METAR report variable wind direction in a clockwise direction?
Does the convention for reporting variable wind direction always use a clockwise (nautical) sense?
For example, if the wind varies between 340 degrees and 10 degrees, assuming a clockwise sense the ...
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1answer
92 views
Is an area of localized reduced visibility considered to be a cloud?
If there an area containing visible moisture in an otherwise clear sky and that area of visible moisture is transparent is it considered a "thin cloud" or simply a "localized area of reduced ...
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1answer
203 views
What is an approved weather source for flying an instrument approach into an airport with no working ATIS?
What can you use as viable weather information landing at an airport with ATIS inoperative due to the tower being closed after hours? Let's assume the approach secondary weather source is also ...
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2answers
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Who makes the call to start in terrible weather conditions?
I once headed to the airport during a huge thunderstorm with winds above 55 knots and massive rain and some small hail. At the airport, I saw that most flights were delayed or even canceled. To my ...
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2answers
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Are helicopters impacted by fog more than airplanes?
With the crash of Kobe Bryant's helicopter, it seems a lot of focus has been placed on the helicopter flying low in fog (under "special VFR"). However, I've seen several suggestions that the ...
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0answers
332 views
How far can the sound of a sonic boom travel? [closed]
Are there conditions or distances from the plane to cloud to the observer in which a sonic boom from a plane is muted?
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2answers
104 views
Why and how do atmospheric properties sometimes vary from the ISA? [closed]
I'm curious as to why sometimes atmospheric properties don't match the ISA's. One reason I am considering is due to calibration discrepancies. By atmospheric properties I mean temperature, Density, ...
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5answers
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Why did my LGA-ORD flight make an S-shaped turn round the time it was passing a storm?
On a recent United UA1709 flight into Chicago (hit by a heavy storm at the time), I felt a noticeable descent, combined with two wide banks around 1 hour before landing. Looking at the flight path, I ...
